1. Field of the Invention
The invention relates to an aeration device for bioreactors with a first aeration element with gas outlet openings of a first size and with at least one second aeration element with gas outlet openings of a second size.
2. Description of the Related Art
Provision of an oxygen supply is a key factor in cellular metabolic processes. Although animal cell cultures consume substantially less oxygen than bacteria and yeast cultures, ensuring an efficient supply is the greatest challenge facing the operation of a cell culture bioreactor. In addition to supplying the cells with oxygen, the concentration of dissolved carbon dioxide also plays a part as a controlled variable.
There are two conventional aeration methods: aerating the headspace of the bioreactor and direct injection of the gases through aeration rings. For this purpose, use is made not only of the aeration rings known from fermenters with bores or gas outlet openings of for example 0.8 mm but also of “microspargers” made from sintered plastics with pore sizes of for example 20 to 45 μm, which likewise form gas outlet openings. Both kinds have specific advantages and drawbacks. The aeration ring produces larger bubbles, which means that higher gas throughput rates are required to achieve the same “oxygen transfer rate”. With its relatively large bubbles, the ring sparger is suitable for stripping or sweeping out CO2 with air, for example. With its relatively small bubbles, the microsparger is particularly suitable for supplying oxygen. One drawback, however, is that under unfavorable conditions foaming may occur due to the relatively smaller bubbles.
Aeration devices are used as part of automated bioreactor aeration systems, for example single-use reactors, the supply of air, oxygen, carbon dioxide and nitrogen being mutually independently controllable. Sensors for oxygen partial pressure and pH facilitate the control of these important process parameters.
WO 2009/122310 A2, WO 2009/115926 A2 and WO 2009/116002 A1 disclose a single-use bioreactor with a mixer and with an aeration device arranged on the bottom of the reactor interior. It is known here to arrange two aeration elements on the bottom which take the form of opposing, mating ring segments.
Drawbacks of this aeration device, which has in principle proved effective, are that, on the one hand, it must be fastened in relatively complex manner to the bottom of the reactor and that, on the other hand, it is difficult to arrange a plurality of such aeration elements optimally relative to the stirrer or mixer.
An aeration device for bioreactors is furthermore known from WO 2008/088371 A2, in which for example two aeration elements with different gas outlet openings may be fastened to the bottom of the reactor.
One drawback here is that the aeration elements are fastened in relatively complex manner to the bottom of the reactor. A further drawback is that the individual aeration element is here not optimally arranged relative to the mixer.
The object of the present invention is accordingly to improve the known aeration devices for bioreactors in such a manner that, on the one hand, they are simpler to fasten and, on the other hand, each aeration element is optimally positioned relative to a mixing element arranged in the reactor interior.